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| author | Alec Theriault <alec.theriault@gmail.com> | 2018-05-08 12:24:26 -0700 |
|---|---|---|
| committer | Ben Gamari <ben@smart-cactus.org> | 2018-05-30 22:05:37 -0400 |
| commit | b57a54f6be600541dbcc4d8489c751a17a85bec0 (patch) | |
| tree | e55fa18e6b06947612b74d8062b14b19fe7c4f12 | |
| parent | 730781b42a003604cfa047a02280757a07b09581 (diff) | |
| download | haskell-b57a54f6be600541dbcc4d8489c751a17a85bec0.tar.gz | |
SplicePat's should not trip -Wunused-pattern-binds
The warning does not consider the fact that the splice pattern may
very well end up binding variables.
| -rw-r--r-- | compiler/rename/RnBinds.hs | 15 |
1 files changed, 11 insertions, 4 deletions
diff --git a/compiler/rename/RnBinds.hs b/compiler/rename/RnBinds.hs index d7790ca419..79b55029a1 100644 --- a/compiler/rename/RnBinds.hs +++ b/compiler/rename/RnBinds.hs @@ -470,9 +470,10 @@ rnBind _ bind@(PatBind { pat_lhs = pat ok_nobind_pat = -- See Note [Pattern bindings that bind no variables] case pat of - L _ (WildPat {}) -> True - L _ (BangPat {}) -> True -- #9127, #13646 - _ -> False + L _ (WildPat {}) -> True + L _ (BangPat {}) -> True -- #9127, #13646 + L _ (SplicePat {}) -> True + _ -> False -- Warn if the pattern binds no variables -- See Note [Pattern bindings that bind no variables] @@ -518,7 +519,7 @@ rnBind _ b = pprPanic "rnBind" (ppr b) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Generally, we want to warn about pattern bindings like Just _ = e -because they don't do anything! But we have two exceptions: +because they don't do anything! But we have three exceptions: * A wildcard pattern _ = rhs @@ -532,6 +533,12 @@ because they don't do anything! But we have two exceptions: Moreover, Trac #13646 argues that even for single constructor types, you might want to write the constructor. See also #9127. +* A splice pattern + $(th-lhs) = rhs + It is impossible to determine whether or not th-lhs really + binds any variable. We should disable the warning for any pattern + which contain splices, but that is a more expensive check. + Note [Free-variable space leak] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ We have |